title: Effect of double bond geometry in sphingosine base on the antioxidant function of sphingomyelin.
abstract: We previously showed that sphingomyelin (SM) inhibits peroxidation of phosphatidylcholine (PC) and cholesterol. Since SM uniquely has a trans unsaturation in its sphingosine base, we investigated whether this feature is important for its antioxidant function. Substitution of the natural trans Delta(4)-double bond with a cis double bond (cis-SM), however, increased SM's ability to inhibit Cu(2+)-mediated 16:0-18:2 PC oxidation by up to eightfold. Dihydro-SM, which lacks the double bond, was equally effective as trans-SM. In contrast to its effect in the sphingosine base, the presence of a cis double bond in the N-acyl group of trans-SM was not protective. cis-SM also inhibited the oxidation of cholesterol by FeSO_(4)/ascorbate more efficiently than the trans isomer. The enhanced protective effect of cis-SM is selective for metal ion-promoted oxidation, and appears to arise from a decrease in the effective concentration of metal ions. These studies show that the trans double bond of SM is not essential for its antioxidant effects.
authors.affiliation: Department of Medicine, Section of Endocrinology and Metabolism, University of Illinois at Chicago, 1819 West Polk Street, Chicago, IL 60612, USA. psubbaia@uic.edu
authors.forename: Papasani V
authors.initials: PV
authors.lastname: Subbaiah
authors.forename: Debajit
authors.initials: D
authors.lastname: Sircar
authors.forename: Ravi S
authors.initials: RS
authors.lastname: Lankalapalli
authors.forename: Robert
authors.initials: R
authors.lastname: Bittman
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000737:chemistry; D002413:Cations, Divalent; D002784:Cholesterol / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D015227:Lipid Peroxidation; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry*; D013110:Sphingosine / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000975:Antioxidants; D002413:Cations, Divalent; D005296:Ferrous Compounds; D010713:Phosphatidylcholines; D013109:Sphingomyelins; C020748:ferrous sulfate; D003300:Copper; D002784:Cholesterol; D013110:Sphingosine; D001205:Ascorbic Acid